Re: optimizer question

Bruce Momjian wrote:
>
> > "Reinoud van Leeuwen" <reinoud(at)xs4all(dot)nl> writes:
> > > I have a table that contains almost 8 milion rows. The primary key is a
> > > sequence, so the index should have a good distribution. Why does the
> > > optimizer refuse to use the index for getting the maximum value?
> >
> > The optimizer has no idea that max() has anything to do with indexes.
> > You could try something like
> >
> > select * from tab order by foo desc limit 1;
>
> Can we consider doing this optimization automatically?

That would be real cool. I don't know of any database that does that. (I do
know that our Oracle 8i does not)

On a side note (can of worms?) is there the notion of a "rule based optimizer"
vs the cost based optimizer in Postgres?